Centrifugal separator for cleaning of a gaseous fluid

ABSTRACT

A centrifugal separator for cleaning of a gas from solid and/or liquid particles suspended therein, includes a stationary housing and a rotor arranged therein. The rotor at its one axial end has a central inlet for gas to be cleaned and delimits a central space communicating with the inlet. Around the central space a stack of conical separation discs is arranged in the rotor. These discs form between themselves several through flow passages which at their one ends communicate with the central space in the rotor and at their other ends communicate directly with a receiving chamber surrounding the rotor in the stationary housing. The rotor supports several turbine blades, which are arranged in a ring around the central inlet of the rotor, and at least one nozzle is adapted to direct a gaseous driving fluid towards the turbine blades for the rotor rotation.

[0001] The present invention relates to a centrifugal separator forfreeing a stream of a gaseous fluid from particles suspended therein,solid and/or liquid, having a density larger than that of the gaseousfluid. Particularly, the invention concerns a centrifugal separator forthis purpose, including

[0002] a rotor, that is rotatable about a rotational axis and has at oneaxial end a central inlet for said stream of a gaseous fluid, the rotorfurther delimiting a central space communicating with said centralinlet,

[0003] a driving means for rotation of the rotor about said rotationalaxis,

[0004] a stationary housing which with a surrounding wall surrounds therotor and said rotational axis and which between the rotor and thesurrounding wall delimits a receiving chamber (44) for cleaned gaseousfluid as well as separated particles,

[0005] stationary inlet means situated at said axial end of the rotorand forming a gas inlet for said stream of a gaseous fluid, whichcommunicates with the central inlet of the rotor, and

[0006] separation members supported by the rotor around said centralspace and forming several separation passages which have inlet endscommunicating with the central space in the rotor and outlet endsopening directly into one part of said receiving chamber.

[0007] A centrifugal separator of this kind is known by EP 0 011 270 A.

[0008] One object of the invention is to provide a centrifugal separatorof the defined kind, having a driving means that makes possible both acompact construction of the whole centrifugal separator and an efficientoperation thereof.

[0009] Another object is to provide a centrifugal separator of thedefined kind, in in which the flow paths for uncleaned and cleanedgaseous fluid and for separated particles extend in a way such that noconflict arises between the requirement of a compact construction andthe requirement of an efficient driving of the centrifugal separator.

[0010] These objects may be obtained in a centrifugal separator of thekind initially defined, that is characterized in that said driving meansincludes several turbine members, which are supported by the rotor andarranged in a ring around the central inlet of the rotor, and at leastone supply member, e.g. a stationary nozzle, that is adapted to receivea stream of a gaseous driving fluid, other than said stream of a gaseousfluid to be freed from particles suspended therein, and to direct thestream of driving fluid towards the turbine members for rotation of therotor about said rotational axis.

[0011] By means of a driving means of this kind the centrifugalseparator may be made very compact, whereby the centrifugal separatorcan relative easily be used even were very little space is available,such as for instance in engine compartments of vehicles. The centrifugalseparator is well suited among other things for cleaning of crankcasegases coming from internal combustion engines. The gaseous driving fluidrequired for the operation of the centrifugal separator may be conductedfor instance through a hose to the centrifugal separator, which meansthat the centrifugal separator does not have to be placed immediatelyclose to the drive source itself, e.g. a compressor or a pressure vesselfor compressed air.

[0012] Preferably, a centrifugal separator according to the inventionalso includes stationary first outlet members forming a gas outlet fromthe receiving chamber for gaseous fluid having been freed fromparticles, and stationary second outlet members forming a particleoutlet from the receiving chamber, separate from the gas outlet, forparticles having been separated from the gaseous fluid.

[0013] A centrifugal separator according to the invention can beoriented in any suitable way. However, particularly good conditions arecreated for taking care of cleaned fluid and separated particles if thecentrifugal separator is oriented with said rotational axis extendingsubstantially vertically and with the inlet for uncleaned gaseous fluidsituated at the upper end of the rotor.

[0014] Preferably, said particle outlet is situated centrally below therotor, substantially aligned with said rotational axis, said gas outletbeing situated between the particle outlet and said part of thereceiving chamber, in which the separation passages of the rotor areopening.

[0015] Advantageously, the stationary housing surrounding the rotor isformed in a way such that driving fluid, having been used for driving ofthe rotor and thus leaving the ring of turbine members, is introducedinto said receiving chamber and then leaves the centrifugal separatortogether with the cleaned gaseous fluid. If the centrifugal separator isused for cleaning of crankcase gases coming from a combustion engine andthe centrifugal rotor is driven by means of compressed air coming from aturbo compressor belonging to the engine, said gas outlet may beconnected to an air intake of the motor combustion room.

[0016] The aforementioned at least one supply member, which shall directthe gaseous driving fluid towards the turbine members on the rotor, maybe arranged in different ways. It is possible to arrange the supplymember in a way such that it directs the driving fluid axially towardsthe turbine members. However, it would be most advantageous to arrangethe supply member or the supply members radially inside or outside thering of rotor turbine members. If two or more supply members are used,they are suitably distributed evenly around the ring of turbine members,so that a balanced load is obtained on the rotor from the forces towhich it is subjected by the driving fluid. If only two supply membersare used, they are therefore arranged at diametrically opposite sides ofthe ring of the turbine members. This is advantageous for the life ofthe bearings, by which the rotor is suspended in a stationary supportingdevice, e.g. the aforementioned stationary housing.

[0017] In a preferred embodiment of the centrifugal separator accordingto the invention the rotor is connected with a central supporting shaftwhich through a bearing device is suspended in a stationary supportingmember, the ring of turbine members on the rotor being arrangedsubstantially in the same axial plane as said bearing device. If thebearing device, in practice, is constituted by two somewhat axiallyspaced bearings, the ring of turbine members is preferably situated in aplane axially in the middle between these two bearings.

[0018] The invention is further described in the following withreference to the accompanying drawings, in which FIG. 1 shows an axialsection through a centrifugal separator according to a preferredembodiment of the invention and FIGS. 2 and 3 show cross sections alongthe lines II-II and III-III, respectively, in FIG. 1. The axial sectionin FIG. 1 is taken along the line I-I in FIG. 2.

[0019] The centrifugal separator shown in the drawings comprises astationary housing 1 consisting of an upper part 2, an intermediate part3 and a lower part 4. The parts are kept together by means of clampingmembers 5 and 6. The upper housing part 2 forms an inlet 7 for a gas orgas mixture to be cleaned by means of the centrifugal separator. Thelower housing part 4 forms both an outlet 8 for gas having been cleanedand an outlet 9 for material having been separated from the gas.

[0020] The intermediate part 3 of the stationary housing forms asurrounding wall surrounding a space within the housing and has, at itsupper end, an annular end wall 10 extending a distance inwardly from thesurrounding wall. Within the housing the annular end wall 10 supports acentral sleeve 11, the interior of which communicates with the abovementioned gas inlet 7 formed by the upper housing part 2. A gasket 12 isadapted to seal between the upper housing part 2 and the sleeve 11.

[0021] The sleeve 11 supports in its said interior, by means of severalsupporting members 13 (see FIG. 2), a central hub 14. The supportingmembers 13 are distributed around the periphery of the sleeve and leavesbetween themselves several passages 15 which at their upper endscommunicate with the aforementioned gas inlet 7.

[0022] On its inside the hub 14 supports a bearing sleeve 16 which, inturn, supports through bearing balls 17 a vertically extending shaft 18.The shaft 18 extends downwardly within the housing 1 and supportstherein a rotor 19. The rotor is rotatable in the housing 1 about avertical rotational axis R.

[0023] The rotor 19 comprises a substantially conical or bowl-formedupper end wall 20 and a lower end wall 21 formed in the same way. Bothend walls 20 and 21 are facing with their concave sides upwardly towardsthe gas inlet 7 of the stationary housing. Between the end walls thereis arranged a stack of conical separation discs 22 (only part of thestack is shown in FIG. 1), which between themselves delimit thininterspaces forming through flow passages 23 for gas to be cleaned inthe centrifugal separator. The end walls 20 and 21 and the separationdiscs 22 are kept axially compressed on the shaft 18 by means of a screw24 and a spring 25.

[0024]FIG. 3 shows a separation disc 22 seen from above with respect toFIG. 1. The disc has a conical outer portion 26 and a central portion 27connected therewith. The central portion has a large number of throughholes 28 situated at some distance from the center of the disc anddistributed therearound. In the assembled rotor 19 (see FIG. 1) theseholes 28 form together with the interspaces between the central portions27 of the discs a central space 28 a, which communicates with theaforementioned through passages 23 between the discs 22. Furthermore,the central portion 27 has a central non-round, in this case hexagonal,opening through which the aforementioned shaft 18 is intended to extend.As can be seen from both FIG. 1 and FIG. 3, the shaft 18 is surroundedby a sleeve 29 extending axially between the rotor end walls 20 and 21.The sleeve 29 has a circular inner cross section but a hexagonal outercross section, so that the outside of the sleeve may be in rotationalengagement with both the separation discs 22 and the end walls 20 and21.

[0025] On the upper side of each disc 22 there are several rib-likeprotuberances 30, which are evenly distributed around the disc centerand which extend across the conical portion 26 of the disc from thecentral portion 27 to the surrounding edge of the disc. Theprotuberances 30 serve both as spacing members between adjacentseparation discs 22 in the rotor and as flow guiding members during theoperation of the centrifugal separator, as will be explained later. Therib-like protuberances extend in a way such on each separation disc thatthey form an angle with the generatrices of the conical portion 26 ofthe separation disc.

[0026] The upper end wall 20 of the rotor has a radially inner portion31, that is formed in one piece with a central sleeve 32 surrounding theshaft 18, and a radially outer portion 33. The radially inner portion 31of the end wall 20 has several through holes 31 a distributed around thecentral sleeve 32 and forming a central inlet of the rotor 19 for gas tobe cleaned. The holes or inlet 31 a communicate with the gas inlet 7 inthe stationary housing part 2 through the interior of the stationarysleeve 11. The radially inner portion 31 of the end wall 20 further hasan annular axial flange 31 b, which surrounds an end portion of thestationary sleeve 11 in a way such that a smallest possible interspaceis present between the flange 31 b and the sleeve 11. If desired, agasket may be arranged in this interspace.

[0027] The radially outer portion 33 of the end wall 20 supports on itsupper side a ring of turbine blades 34, extending concentrically withthe rotational axis R of the rotor (see FIG. 2). The blades 34 arearranged in a downwardly facing annular groove on the underside of theend wall 10, formed between two downwardly directed annular,concentrical flanges 35 and 36. The ring of turbine blades, thus, aresupported on the radially largest portion of the rotor.

[0028] As can be seen from FIG. 2, the two flanges 35 and 36 do notextend circularly all the way around the rotational axis R of the rotor.Thus, the outer flange 35 has two interruptions or gaps 37 and 38,whereas the inner flange 36 has one interruption or gap 39. Supported bythe intermediate part 3 of the stationary housing a nozzle 40 extendsinto the first said interruption or gap 37 and is adapted to receive apressurized gas and to direct the flow of this gas towards the ring ofturbine blades 34 from the outside of the ring. The nozzle 40 isdirected such that the gas flow will bring the blades 34 and, thereby,the whole of the rotor 19 into rotation about the rotational axis R,counter clockwise with respect to FIG. 2.

[0029] The blades 34 are somewhat curved, as can be seen, although thisis not necessary, and they conduct the gas stream supplied between theadjacent blades to the inside of the ring of blades, where the gasstream enters a small return chamber 41. This return chamber 41 isdelimited between, on the one side, a returning member 42 constitutingpart of the stationary end wall 10 and a plate 42 a fixed to theunderside of the end wall 10 and, on the other side, the ring of turbineblades 34. The return chamber is formed in a way such that the gasentering into it from the interspaces between the turbine blades isconducted without substantial pressure loss in a curved bath a distanceforwards in the rotational direction of the turbine blades to a certainposition and, then, again in between the turbine blades 34 present atthis position. In this way the pressurized gas is used once more fordriving of the ring of turbine blades 34.

[0030] When the pressurized gas has again passed through the ring ofturbine blades 34, it flows radially outwardly through the interruptionor gap 38 in the flange 35 to an annular space 43 in the intermediatepart 3 of the stationary housing (see FIG. 1). This space 43communicates directly with a receiving chamber 44 surrounding the rotor19 in the stationary housing 1.

[0031] As can be seen from the drawings, the part of the housing 1surrounding the rotor 19 is substantially rotationally symmetrical andit has a shape substantially adapted to the outer shape of the rotor.The outlet 8 for cleaned gas is situated in a conical portion of thehousing part 4 at the same axial level as the lower rotor end wall 21.The outlet 9 for material separated from supplied uncleaned gas issituated centrally below the rotor 19 aligned with the rotational axis Rof the rotor.

[0032] As can also be seen from the drawings (see particularly FIG. 2)the returning member 42 is formed in one piece with and substantially atthe same axial level as the sleeve 14 which on its inside supports thebearings 16, 17 for the rotor shaft 18. The returning member 42 therebyis situated radially between the bearing 16, 17 and the turbine blades34. This gives the centrifugal separator a very compact constructionwith respect to the arrangement for the driving and journalling of therotor.

[0033] The above described centrifugal separator operates in thefollowing manner.

[0034] For rotation of the rotor 19 the nozzle 40 is charged from asource, not shown, with pressurized gas, e.g. compressed air. A gasstream is directed by the nozzle 40 from a gas supply area, formed bythe gap 37 in the flange 35 radially outside the ring of turbine blades34, towards the outside of this ring, so that the gas flows between theblades and brings them, and thereby the rotor 19, into rotation counterclockwise with respect to FIG. 2.

[0035] Driving gas coming out from the blade interspaces on the insideof the blade ring enters the return chamber 41, in which it is deflectedforwardly in the rotational direction of the blade ring and then isagain directed towards the blades 34 for renewed driving thereof. Afterhaving been used twice for driving of the turbine blades the gas comesout through the gap 38 in the flange 35 into the space 43 (see FIG. 1),from where it flows further on out into the receiving chamber 44surrounding the rotor 19.

[0036] A contaminated gas to be cleaned from solid and/or liquidparticles suspended therein is supplied through the gas inlet 7 in thestationary upper housing part 2. The gas flows further on through thepassages 15 and the rotor inlet 31 a into the central space 28 a in therotor 19. From the central space 28 a the contaminated gas flows furtherthrough the flow passages 23 between the conical portions 26 of theseparation discs 22.

[0037] Between the separation discs 22 the contaminated gas is broughtinto rotation by the rotor, particles present in the gas and having adensity larger than that of the gas being separated as a consequence ofthe centrifugal force and being brought into contact with the uppersides of the conical portions 26 of the separation discs. In contactwith these portions of the separation discs the particles move as aconsequence of the centrifugal force radially along generatrices of theportions 26, the particles, or coalesced liquid particles, beingcollected by the inclined ribs 30. The separated particles are moved bythe centrifugal force further on along the ribs 30 to thecircumferential edges of the separation discs, from where they arethrown away from the discs and hit the surrounding wall 3 of thehousing.

[0038] The gas successively freed from particles flows between theadjacent separation disc 22, guided by the ribs 30, towards thesurrounding edges of the discs and leaves the rotor at these edges.Through the receiving chamber 44 the cleaned gas flows out of thehousing 1 through the outlet 8. This outlet 8, as can be seen, is placedbelow the level at which particles separated from the gas are thrownaway from the rotor 19 towards the surrounding wall 3. Also the gashaving been used for driving of the rotor leaves the stationary housingthrough the outlet 8.

[0039] Due to the fact that the contaminated gas enters the centralspace 28 a in the rotor 19 substantially without rotational movement,whereas the cleaned gas leaves the rotor under rotation at a radiuslarger than the radius of the central space 28 a, an underpressure willarise in the central space 28 a. Hereby, the contaminating gas need notbe supplied to the rotor at an over pressure. Instead, it may be suckedinto the rotor from the gas inlet 7 of the stationary housing 1.

[0040] The particles separated from the gas, solid and/or liquid, movedownwardly along the inside of the surrounding wall 3 and further alongthe conical lower part of the housing 1 and out through the outlet 9. Bythe shape as shown in FIG. 1 of the outlet pipe forming the outlet 8,i.e. by the fact that this outlet pipe extends a short distance into theinterior of the housing 1 and is provided with a flange, it is avoidedthat separated particles are entrained with cleaned gas out through theoutlet 8.

1. A centrifugal separator for freeing a stream of a gaseous fluid fromparticles suspended therein, solid and/or liquid, having a densitylarger than that of the gaseous fluid, including a rotor (19), that isrotatable about a rotational axis (R) and has at one axial end a centralinlet (31 a) for said stream of a gaseous fluid, the rotor furtherdelimiting a central space (28 a) communicating with said central inlet(31 a), a driving means for rotation of the rotor (19) about saidrational axis R, a stationary housing (1) which with a surrounding wall(3) surrounds the rotor (19) and said rotational axis (R) and whichbetween the rotor and the surrounding wall delimits a receiving chamber(44) for cleaned gaseous fluid as well as separated particles,stationary inlet means (2) arranged at said axial end of the rotor (19)and forming a gas inlet (7) for said stream of a gaseous fluid, whichgas inlet (7) communicates with the central inlet (31 a) of the rotor,and separation members (22) which are supported by the rotor around saidcentral space (28 a) and which form several separation passages (23)having inlet ends communicating with the central space (28 a) in therotor and outlet ends opening directly in a part of said receivingchamber (44) between the rotor and said surrounding wall, characterizedin that said driving means includes several turbine members (34), whichare supported by the rotor (19) and arranged in a ring around thecentral inlet (31 a) of the rotor, and at least one supply member (40)that is adapted to receive a stream of a gaseous driving fluid, otherthan said stream of a gaseous fluid to be freed from particles suspendedtherein, and to direct the stream of driving fluid towards the turbinemembers (34) for rotation of the rotor about said rotational axis (R).2. A centrifugal separator according to claim 1, in which thecentrifugal separator includes also stationary first outlet members,which form a gas outlet (8) from the receiving member (44) for gaseousfluid having been freed from particles, and stationary second outletmembers forming a particle outlet (9) from the receiving chamber (44),separated from the gas inlet (8), for particles having been separatedfrom the gaseous fluid.
 3. A centrifugal separator according to claim 1or 2, in which the rotor (19) is oriented such that said rotational axis(R) extends substantially vertically.
 4. A centrifugal separatoraccording to claim 3, in which the central inlet (31 a) of the rotor issituated at the upper axial end of the rotor.
 5. A centrifugal separatoraccording to claim 3, in which said gas outlet (8) is situated belowsaid part of the receiving chamber (44) in which the separation passages(23) open with their outlet ends.
 6. A centrifugal separator accordingto claim 4 or 5, in which said particle outlet (9) is situated centrallybelow the rotor (19) substantially aligned with said rotational axis(R).
 7. A centrifugal separator according to claim 6, in which thestationary housing (1) is tapering substantially conically towards theparticle outlet (9).
 8. A centrifugal separator according to claim 7, inwhich the gas outlet (8) is situated in the conically tapering part ofthe stationary housing (1).
 9. A centrifugal separator according to anyone of the preceding claims, in which said separations members includesstack of conical separation discs (22) arranged coaxially with saidrotational axis (R) and forming said separation passages (23) betweenthemselves.
 10. A centrifugal separator according to claim 9, in whichthe conical separation disc (22) have apex ends and base ends, said baseends of the discs facing axially towards said central inlet (31 a). 11.A centrifugal separator according to claim 9 or 10, in which eachconical separations disc (22) has several central through openings (28)forming together with interspaces between the separation discs saidcentral space (28 a) in the rotor.
 12. A centrifugal separator accordingto any one of the preceding claims, in which the stationary housing (1)is formed such that driving fluid, that leaves the ring of turbineblades (34), is conducted into said receiving chamber (44).
 13. Acentrifugal separator according to claim 12, in which a space (43)surrounding the ring of turbine members (34) and adapted to receivedriving fluid having been used for driving of the rotor (19)communicates with said receiving chamber (44).
 14. A centrifugalseparator according to any one of the preceding claims, in which therotor (19) at its axial end having said central inlet (31 a) has abowl-formed end wall (20) having a concave outside, the ring of turbinemembers (34) being supported at a radially outer edge portion of saidbowl-formed end wall.
 15. A centrifugal separator according to claim 14,in which separation members supported by the rotor include a stack ofconical separation discs (22) having apex ends and base ends, the baseends facing axially towards said bowl-formed end wall (20).
 16. Acentrifugal separator according to any one of the preceding claims, inwhich the rotor is connected with a shaft (18) that through a bearing(16, 17) is supported by a stationary supporting member (14), said gasinlet extending through an annular area (15) around the rotational axis(R), situated between the stationary supporting member (14) and the ringof turbine members (34).